Go through the Dragon door

As an adventurer, you've vanquished your fair share of dragons, so one more shouldn't be too difficult. You step through the doorway into a long, stone corridor stretching to the left and to the right. A quiet grinding noise fills the corridor, and you turn to find that the doorway has disappeared. There's no going back, apparently.

Both directions look the same, but you're lacking a coin to flip at the moment.